Lap



Patented May 28, 1946 UNITED STATE-S` PATENT OFFICE.v

LAP

AntonAnderson, Chicago,.1ll. Application January 9, 1945,4 Serial No.,572,063

' Claims.

cal barrel with longitudinal slits. arranged tan-` gentially or at anangle to the radius of the cylinder whereby the segments between thesl'itswill have a desired degree ofY resiliency; to provide a.

lap which will have a relatively fast abrading action when rotated inone direction and a smoothing or polishing action when rotated in theopposite direction; and to provide such other improvements inconstruction and advantages in operation as will appear from thefollowing description.

In the accompanying drawing showing this invention,

Fie. 1 is a side View of the lap;

Fig. 2 is an enlarged longitudinal sectional view;

Fig. 3 is a cross section taken substantially on the line 3 3 ofFig. 2;

Fig. 4 is an enlarged cross section. showing the operation of the lapwhen turned in the direction to cause rapid abrasion; and

Fig. 5 is a View similar to Fig. 4 showing the lap rotating inrelativelyopposite direction or in reversed position in the hole as for polishingpurposes.

As shown in this drawing, the lap has a shank or stem portion I0 whichis adapted to be held in a drill or other suitable machine tool foroperating the same. AThis shank has a reduced threaded connection IIwhich is engaged by a correspondingly threaded end I2 of the main cy`lindrical portion or barrel I3 of the lap. The ends of the barrel areprovided with tapered or conical bores or recesses I4 and I5 which mayconveniently be tapered at an 8 included angle. The inner ends oi thesebores terminate at a cross wall I6 which is pierced with a hole Illeaving annular shoulders I3 extending inwardly at approximately thecenter of the barrel.

The barrel is provided with a plurality of substantially longitudinalcuts or slits I9 which extend to points adjacent to the threaded ends ofthe barrel. These slits may be milled, sawed, or

cut in any desired mannen, and the arrangement thereof forms one of thenovel features of this inventionl Instead. of being radially arranged.as has been heretofore proposed, these slits, are at an angle totheradiusV or as shown in. the present instance, are substantiallytangential to the walls of the hole I7. These slits form expansibl'e`longitudinal segments 2Q., the outer surfaces of.A which provide theworking areas of the lap The. positioning of the slits in this mannerprovides narrow lands 2l on each of the segments around the hole Il.

The segments or sidesv of the lap are adjusted by means of a taperedadjusting pin 22 which is adapted to enter the hole I'I and engage withthe landsr 2l.. This pinhasf an enlarged threaded portion 23 thatengages with a corresponding.- ly threaded end 24 of the barrel. Thisis" pref.- erably a left hand thread for reasons which will presently bedescribed. The outer end 25 of the pin is flattened or otherwise shapedfor engagement. by a wrench or adjusting tool. When this which passoutside of the working surface A26 of the corresponding lap, andconsequently pressure exerted on the land by the pin is not` exerteddirectly or radially against the working surface of the segment.Likewisel pressure which is exerted on the working surface when thelapis in operation is not transmitted radially or directly against the pin,The land 2I may be considered as a fulcrum or bearing and when pressureis exerted against the outer or working surface of the segment, it willbe resisted only by the twisting or torsional action of the segment, andtherefore will have suflicient spring or resiliency to accomplish thedesired results. The ends of the segments or longitudinal strips beingrelatively thin Will assist in permitting this torsional or resilientmovement. The greater thickness of the segments or engaging elements atthe center will provide for more wear as it is in such portions that theprincipal amount of work is done and the wear is greatest in this area.

When the lap is to be used, the shank is inserted in the drill ormachine tool in the usual manner and the adjusting pin is screwed in toexpand the segments to the desired diameter. The abrading material isapplied in the usual manner and the lap is inserted in the hole asindicated at 21 in a work piece 28 which is to be lapped. If the lap isrotated in the direction indicated by the arrow in Fig. 4, the pressureon the segments will tend to swing the forward edges inwardly and thuspermit more abrasive to enter the spaces between the segments and thewalls of the hole. This operation serves for rapid abrasion or grinding.The adjusting pin 22, as above stated, is preferably provided with lefthand thread 6 so that if the projecting tang 25 comes in Contact withthe bed of the drill, it will tend to unscrew or loosen the same, ratherthan to increase the pressure. If the movement of the lap is reversed asshown in Fig. 5, as by reversing the position of the lap in the drill,the leading edges of the segments which Contact closely with the wallsof .the hole will tend to wipe away the abrasive and provides means forgiving a smooth-` ing action or smooth nish.

From this description, it will be seen that I provide a lap of simpleconstruction having a single solid expanding pin acting against seats orbearings at substantially the middle of the lap whereby the abradingmembers may be uniformly expanded to provide a substantiallybarrel-shaped or curved working surface. Each segment has a cushion orresilient action which is inherent in the construction of the lap, anddoes not require-additional tension members, springs, or the like. Thiscushioning is created by a twisting or rotating-of the mid-portion ofeach lap segment with respect to the cylindrical uncut ends of the lapbarrel.

My improved laps may be formed of any suitablematerial, but arepreferably'made of soft or mild steel such as commonly used for thispurpose.

While I have shown a preferred form ofr my invention, it is my intentionthat the same may be modified as for different sizes or classes of workwithout departing from the scope of the invention as set forth in thefollowing claims in which I claim:

l. A lap having a cylindrical barrel kwith an inwardly extending annularprojection with a central hole therethrough, the walls of the barrel andsaid projection having a plurality of longitudinal slits substantiallytangential to said hole forming working segments and also forming landsterminating at the circumference of said hole and means coacting withsaid lands to expand the segments.

2. A substantially cylindrical lap barrel having longitudinal slitswhich terminate at a distance from the ends of the barrel, to provideworking segments, inwardly extending lands on said segments the innerends of which terminate at the circumference of a central hole and,which are positioned circumferentially substantially beyond the radiiembracing the outer face of the respective segment, whereby they areoiset circumferentially with respect to the outer faces of the segments,said slits being arranged tangentially to said hole, and non-resilientadjusting means coacting with said lands for expanding the segments, thearrangement being such that the segments will have a torsionallyresilient action when in use.

3. In a device of the character set forth, the combination of a stem, alap barrel having Vthreaded engagement with said stem, the Walls of thebarrel increasing in thickness towards the center thereof, an annularprojection extending inwardly at the center and having a holetherethrough, slits arranged substantially tangentially to said hole andterminating short of the ends of thefbarrel and dividing the barrel intoa plurality of working segments, a tapered adjusting pin having threadedengagement with the opposite end of the barrel and projecting throughsaid hole and adapted to spread the working segments.

4. In combination, a stem, a lap barrel having threaded engagement withthe stem and having conical bores extending inwardly from the endsthereof, an annular projection extending inwardly at substantially thecenter of the barrel and having a hole therethrough, said barrel havinga plurality of longitudinal cuts through the walls thereof extending topoints adjacent the ends of the barrel and extending through saidprojection, said cuts being arranged substantially tangentially to saidhole, whereby lands are provided on each segment, a tapered adjustingpin having threaded engagement with the opposite endof the barrel andcoacting with said lands for expanding the working segments, substan-

